# Homework Help: Electric Field Question Help! (don't know how to get started)

1. Jan 18, 2012

### pierretong

1. The problem statement, all variables and given/known data

Two point charges q1 = 8.10×10-5 C and q2 = 3.24×10-4 C are separated by a distance d = 0.10 m. Compute their net electric field E (x) as a function of x for the following positive and negative values of x, taking E to be positive when the vector E points to the right and negative when E points to the left.

Diagram shows 2 charges q1 and q2 (q1 is on the origin, q2 is distance d to the right along the x axis.

a)What is E(-0.100)?
b)What is E(-0.050)?
c)What is E(-0.010)?

etc....

2. Relevant equations

E = kQ/r^2

3. The attempt at a solution

no idea where to start this problem. I know how to calculate the electric field but I don't get what it means when it says "as a function of x" (what is x? there is no x on the diagram, just 2 point charges and the distance between them).

If someone could walk me through a, I could do the rest! Thanks!

2. Jan 18, 2012

### Staff: Mentor

x is just the position along the x-axis, measured from q1 (the origin, where x = 0). For example, charge q2 is at x = d = 0.10 m.

3. May 14, 2012

### arl146

i dont get it .. do you use the x in place of the r and does q1 stay at the origin? im really confused on the x concept

4. May 15, 2012

### Staff: Mentor

"x" just represents any point along the x-axis. The positions of the charges remain the same.

If you want the field at x = - 0.100, then you have to figure out the distances from that point to the charges in order to compute the field at that point.